Plastic lenses are lightweight, less fragile, and dyeable, as compared with inorganic lenses. For these reasons, plastic lenses for use in eyeglasses and sunglasses have become widespread. A variety of resins have heretofore been developed and used. Representative examples among them include allyl resins obtained from diethylene glycol bis-allyl carbonates and diallyl isophthalates, and (meth)acrylic resins obtained from (meth)acrylates. Examples of higher refractive index resins include thiourethane resins obtained from isocyanates and thiols (Patent Document 1).
In recent years, attention has been focused on a thermoplastic resin which is a recyclable material, as an Earth-friendly eco-material. A thermoplastic resin exhibits being readily moldable from pellets and therefore affords high productivity, which can significantly contribute to the reduction in costs of products. Due to the transportability of a thermoplastic resin in the form of pellets, it is possible to reduce the safety risk as compared with the case of transferring liquid monomers.
A urethane resin (TPU) consisting of a bifunctional isocyanate and an alcohol is known as a thermoplastic resin. Further, a urethane urea resin having a higher heat resistance than a urethane resin, and consisting of a bifunctional isocyanate, an alcohol and an amine has been developed (Patent Documents 2 to 5).